The present invention relates to a medium transporting device which transports a medium and a recording apparatus provided with this medium transporting device.
Heretofore, for example, in an ink jet printer that is one of recording apparatuses, while paper that is one of recording media is being fed into a recording section by a paper transporting device, recording is performed and thereafter the paper is fed out to the outside. In such the ink jet printer, while the paper is fed in a state where it is held between a feed roller and its driven roller, recording is performed in a recording head, and thereafter the paper is fed out in a state where it is held by a discharge roller and a spur roller functioning as its driver roller, and discharged.
In the ink jet printer including such the paper transporting device, in case that an image composed of ejected many ink droplets, for example, a solid image is recorded on the paper, the paper absorbs a large amount of ink, so that it bulges toward the recording head in the wavy shape after recording, that is, cockling is produced. As this cockling develops, the distance between the paper and the recording head becomes more uneven, and unevenness is produced in ink splash distance, whereby unevenness is produced in recording, or the paper comes into contact with the recording head and stains. Therefore, recently, an ink jet printer has been proposed, in which plural openings are formed on a paper transporting surface in the paper transporting direction and in the direction perpendicular to the paper transporting direction at a regular pitch, that is, the plural openings are provided in the shape of a grid, and the paper is sucked through these opening by a suction pump thereby to suppress the above cockling (refer to JP-A-63-303781 and JP-A-3-270).
Generally, a curve (curl) is produced in paper by the influence of environment such as humidity and temperature, or by properties of surface coat material. Particularly, it is most difficult to suck and attract ends (a leading end and both side ends) of the paper which has curled upward. Therefore, there is fear that the ends of the paper which has curled are stained by contact with the recording head.
Further, by setting of a position of a feed roller arranged in a paper transportation-insertion part of the above paper transporting device, it is possible to press the leading end of the inserted paper on the paper transporting surface thereby to prevent coming-up of the leading end. However, as the paper advances, the power for pressing mechanically the leading end of the paper on the paper transporting surface is reduced, so that the leading end of the paper readily separates from the paper transporting surface. Therefore, there is fear that the leading end of the paper which has come up is stained by the contact with the recording head.
In the ink jet printers including the above conventional suction type paper transporting device, there is an ink jet printer having a dimple around each opening in order to heighten suction force determined by negative pressure×area. However, since the dimples are formed in the shape of a grid correspondingly to each opening, both ends of the paper in a direction perpendicular to the paper transporting direction, that is, both side ends of the paper get on partition walls formed outside the dimples corresponding to the both side ends of the paper. Therefore, the both side ends of the paper readily curl up by the suction force of holes in the dimples corresponding to the both side ends, and there is fear that the both side ends are stained by contact with the recording head.